Condensation of metal vapors



of product.

Patente d Apr. 22, 1941 &238.907

CONDENSATION OF METAL VAPORS Thomas B. McConic., III, and Charles E.Nelson, mund, mich., asignors to The Do' Chemical Midiand, Mich., acorporation ot Application January 31, 1940, Serial No. 316,628

12 Clain.

This invention concerns an improved method of condensing metal vapors.In its preferred form, it relates to condensing magnesium fromvapor-phase mixtures also containing carbon monoxide. i

In the production of metallic magnesium by the thermal reduction 'ofmagnesia-containing ores with carboniferous reducing agents, themagnesium is formed in the vapor phase in admixture with carbonmonoxide, and is recovered as solid metal by condensation. As is wellknown, in the condensation step the magnesium vapors must be cooled to alow temperature as rapidly as possible in order to avoid interaction ofthe magnesium and carbon monoxide at the more elevated temperatures; Ithas been suggested that this rapid cooling' be accomplished bycontacting the magnesium carbon monoxide mixture issuing from thereaction zone with a cold condenser* surface, by injecting cold fluidssuch as hydrogen or kerosene into the metalvapor mixture, 'and even byblowing finely-divded fusible salts into the vapor stream. However,because of inherent Operating disadvantages, most of which are discussedin the art, none of these methods has met with widespread acceptance.

An object of the present invention, then, is to provide a simple methodfor cooling and condensing metal vapors, particularly magnesium vaporsadmixed with cabon monoxide, with high thermal emciency and with minimumloss Another object is to provide such a method wherein the Volume ofnon -condensable vapor to be handled is at a minimum. A further objectis to permit of the recovery of the condensed metal in the form ofrelatively large particles.

According to the invention, metal vapors are cooled rapidly andcondensed by contacting them with relatively cool metal particles,preferably in a quantity sumcient to absorb the heat of condensation andcooling without themselves fusing. i

The invention may best be understood by referring to the accompanyingdrawing, which illustrates in diagrammatic section one form of apparatusadapted to condensing metal vapors. The process will, for purpose ofillustration, be explained with reference to the condensation ofmagnesium from vapor mixture thereof with carbon monoxide, using finelydivided magnesium powder as condensing agent, although it wiil beappreciated that the inventlon is not thus limited.

The mixture or magnesium vapors and carbon monoxide resulting !rom thethermal reduction of magnesia-containing ores-leaving the reaction zoneenters the apparatus through a vapor tube I leading to a mixing chamber2 constructed of brick or other refractory material; Cold finely-dividedmagnesium powder rrom a hopper 3, controlled by a valve l, falls or isblown into the mixing zone from a chute 5, either by the force or'gravity, the action of a suitable mechanical impeller (not shown), orthe pressure oi an inert gas, such as hydrogen, supplied in smallquantities through an inlet E., This inlet also serves to admit make-upmagnesium powder, as hereinafter explained. In the chamber 2, themagnesium vapor and carbon monoxide are mixed intimately with the coldmagnesium powder, which coolsand condenses the vapor. leaving asuspension of solid magnesium particles in carbon monoxide. Thissuspension is withdrawn through a conduit 'I to the inlet i of a blowera. This blower forces the gaseous suspension through a coler !0surrounded by a jacket ll, through which water can be circulated by wayof nipples' z. The cold suspension from the cooler III is 'blowntangentially into a centrifuga Separator !3, in which the metalparticles are separated from the carbon monoxide, the latter escapingthrough a central gas outlet ll. The Separator is of such design thatthe heavier particles of magnesium are thrown to the walls, fall intothe conical bottom IS ot the Separator, and are removed through thechute IS. The lighter or finer particles of magnesium collect in thehopper 3 near the center of the Separator, and re-enter the processthrough the chute 5, together with make-up particles added through theinlet G to replace those withdrawn.

In operation, the magnesium vapor-carbon monoxide mixture leaves thereduction zone and enters the mixing chamber 2 at a temperature of'lO00-2000 C. and is condensed and cooled by contact with magnesiumpowder to a temperature below 650 C., and preferably much.

lower, say 200 C. To this end, the finely-di vided magnesium powder issupplied preferabiy at about room temperature (25 C.) and preferablyin aquantity sumcient t absorb the heat of condensation and cooling. Ingeneral, sevp eral parts by weight of nagnesium powder are required perpart of magnesum condensed. The cooler n serves to reduce thetemperature of the magnesium powder-carbon monoxide susroom temperature,separating the mgnesium particles from the carbon monoxide, and returning `at least part or the particles so separated to the first step ofthe process.

10. 'I'he process of cooling and condensing magnesium from vapor phaseadmixture with carbon monoxide at a .temperature of at least 1000" C.,which comprises injecting into said mixture' flnely-divided magnesiumpowder supplied at approximately room temperature and in a.

quantlty at, least -sumcient to abs'orb the heato iberated in condensingthe magnesium and cooling the mixture to a temperature below 650 C.,whereby the magnesium condenses' on the surface of some of the panticlesof the powder and there is formed a suspension of fine and rela.- tivelycosi-se particles of magnesium in carbon monoxide at, a temperaturebelow 650? C.. cooling the suspension to` approximately roomtemperature, simultaneously separatihg' the magnesium particles from thecarbon monoxide and the fine particles from the relatlvely coarseparticles, withdrawing the course paftlcles, and retummg the nneparticles to the first step of the process.

11. The' process of condensing a metal from a vapor state whichcomprises injectlng into :the metal vapor a stream of relativeiy coolmetal particles. i

12.' The process ot condensing a metal from the vapor state whichcomp'rises injectng into the metal vapor a stream of relatively coolflnelydivided metal powder Suspended in a small proportion o! a gaschemically inert to the powder.

THOMAS H. MCCONICA, III. CHARLES E. NELSON.

